4. Wind Turbines at Horns Rev 3
4.3 Lightning and marking
The wind turbines will exhibit distinguishing markings visible for vessels and aircrafts in accord-ance with requirements by the Danish Maritime Authority (Søfartsstyrelsen) and the Danish Transport Authority (Trafikstyrelsen).
Horns Rev 3 will be marked on the appropriate aeronautical charts as required by the Danish Transport Authority. It will also be lit in a way that meets the requirements of both aviation (civil-ian and military) and marine stakeholders. Lighting will be required to make the development visi-ble to both aircrew and mariners. It is likely that two separate systems will be required to meet aviation standards and marine safety hazard marking requirements.
The light markings for aviation as well as the shipping and navigation will probably be required to work synchronously. Whether the lightning for Horns Rev 3 OWF will be required to work synchro-nously with Horns Rev 2 and Horns Rev 1 OWFs, should be agreed with the Danish Maritime Au-thority and the Danish Transport AuAu-thority.
The final requirements in relation to lighting will be determined by the Danish Maritime Authority (Søfartsstyrelsen) and the Danish Transport Authority (Trafikstyrelsen) when the layout and height of the wind farm has been finally agreed.
4.3.1 Marking for ship and navigation
The marking with light on the turbines in relation to shipping and navigation is expected to comply with the following description, but must be negotiated between the concessionaire and the Danish Maritime Authority (Søfartsstyrelsen) when the final park layout has been decided, and in due time before construction.
- All turbines placed in the corners and at sharp bends along the peripheral (significant pe-ripheral structures = SPS) of the wind farm, shall be marked with a yellow light. Additional turbines along the peripheral shall be marked, so that there will be a maximum distance between SPS defined turbines on 2 nautical miles.
- The yellow light shall be visible for 180 degrees along the peripheral and for 210-270 de-grees for the corner turbines (typically located around 5-10m up on the transition piece).
The light shall be flashing synchronously with 3 flashes per 10 second and with an effec-tive reach of at least 5 nautical miles. Within the wind farm the individual turbines will not be marked.
- The top part of the foundation (the transition piece) must be painted yellow. Each turbine should be numbered (identification number) using of black number on a yellow back-ground. The identification numbers should differ from the numbers used in Horns Rev 2 OWF. Indirect light should illuminate the part of the yellow painted section with the turbine identification number.
- The marking of Horns Rev 3 OWF is not expected to be synchronized with Horns Rev 2 OWF.
- Demand by the Danish Maritime Authority for Racon on the north side of Horns Rev 3 OWF must be expected.
- The marking with light on the transformer station will depends on where the platform is lo-cated in connection with the turbines. The position of the platform is fixed, whereas the layout of the wind farm will be determined by the coming developer. The platform can be situated within the wind farm, respecting the corridor for export cable etc., or outside the wind turbine array. If the transformer platform is located outside the wind farm area it will most likely be requested to be marked by white flashing lanterns, and an effective reach of 10 nautical miles. The exact specifications of the marking will be agreed with the Danish Maritime Authority in due time before construction.
- There must be a 500 m safety zone around the wind farm and around the transformer platform, if the platform is not located as an integral part of the wind farm.
- During construction the complete construction area shall be marked with yellow lighted buoys with a reach of at least 2 nautical miles. Details on the requirements for the posi-tions and number of buoys shall be agreed with the Danish Maritime Authority
(Søfartsstyrelsen). If cranes of 100-150m height will be used during construction, these shall be marked with fixed red light of low intensity (10 candela as a minimum).
4.3.2 Aviation markings
Aviation markings will be agreed with the Danish Transport Authority (Trafikstyrelsen). Regula-tions on aviation markings of wind turbines (BL 3-11 af 21/03/2013) provide some details on the requirements to aviation markings. The requirements for aviation markings of wind turbines will differ from different types of wind turbines depending on the height of the wind turbine.
Danish regulation and guidance specifies that all turbines in an offshore wind farm with tip heights in excess of 100 m, and not in the vicinity of an airfield, shall be marked with two fixed aviation warning lights at the top of the nacelle. The colour of the lights shall be red with a low-intensity of 10 cd in accordance with type A as detailed in the ICAO guidance. The aviation lights shall be visi-ble horizontally in all directions (360 degrees) regardless of the position of the blades. Besides turbine towers, flashing obstacle warning lights must be placed on turbine nacelles every 900 m along the perimeter, and in all corners and bends of the wind farm. For offshore wind farms with turbine heights between 100 m and 150 m the colour of the lights must be red with a medium-intensity of 2,000 cd (type B) as specified by ICAO. Alternative aviation markings can be negotiat-ed.
Offshore wind farms with turbines whose tip heights are greater than 150 m shall be equipped with obstacle warning lights in accordance with the regulations or based on an individual risk as-sessment. Alternative markings in accordance with the regulations can be negotiated during on-going consultation with appropriate stakeholders as the design phase of Horns Rev 3 progresses.
Towers on the perimeter, corners and bends will be marked by three fixed red obstacle warning lights (type B with a light intensity of 32 cd) placed at an intermediate level of the turbine tower as well as two flashing obstacle lights on top of the nacelle. The colour of the obstacle warning lights during daylight will be white with a medium-intensity of 20,000 cd (type A). At night they will be red with a medium intensity of 2,000 cd (type B). Furthermore the perimeter of the na-celles of these turbines shall be marked by three fixed low intensity red warning lightings each of 32 cd. The distance between the unmarked part of the turbines or tip of the blades and the top of the obstacle markings must not exceed 120 m.
4.3.3 Operational airborne noise emissions
There are two types of noise associated with wind turbines; aerodynamic noise and mechanical noise.
Aerodynamic noise is broad-band in nature, relatively unobtrusive and is strongly influenced by incident conditions, wind speed and turbulence intensity. An operational Sound Power Level is ex-pected in the order of 95dB(A) to 112dB(A), depending on the selected turbine type and the wind speed.
Mechanical noise is generated by components inside the turbine nacelle and can be radiated by the shell of the nacelle, blades and the tower structure. Such noise emissions are not considered sig-nificant for the present generation of turbines to be considered for the Horns Rev 3 OWF.
Noise levels on land during the operation of the wind farm are expected to be well below allowed limits. The overall limits for operational noise on land according to the Danish legislation are:
44 dB for outdoor areas in relation to neighbours (up to 15m away) in the open land, and
39 dB for outdoors areas in residential areas and other noise sensitive areas.
In relation construction noise, the most extensive noise is normally generated from piling of off-shore foundations. A typical range that can be expected from piling at the source level, is normally within a range of LWA: 125-135 dB(A) LWA re 1pW.
Although offshore contractors have varying construction techniques, the installation of the wind turbines will typically require one or more jack-up barges. These vessels stand on the seabed and create a stable lifting platform by lifting themselves out of the water. The area of seabed taken by a vessels spud cans is approximately 350m2 (in total), with leg penetrations of up to 2 to 15m (depending on seabed properties). These foot prints will be left to in-fill naturally.
The wind turbine components will either be stored at an adjacent port and transported to site by support barge or the installation vessel itself, or transported directly from the manufacturer to the wind farm site by barge or by the installation vessel. The wind turbine will typically be installed using multiple lifts. A number of support vessels for equipment and personnel jack-up barges may also be required.
It is expected that turbines will be installed at a rate of one every one to two days. The works would be planned for 24 hours per day, with lighting of barges at night, and accommodation for crew on board. The installation is weather dependent so installation time may be prolonged in unstable weather conditions.
Following installation and grid connection, the wind turbines are commissioned and are available to generate electricity.